The present invention is directed to trim position sensing apparatus for marine propulsion devices such as outboard motors and the like.
Outboard motors, stern drives and the like are pivotally mounted to the transom of a boat. Relatively large motors are provided with automatic trim positioning controls for adjusting the angular orientation of the outboard motor about a horizontal axis. It is well-known that proper angular orientation or trim of the outboard lower unit is extremely important to provide optimum propulsion of the watercraft and particularly at maximum speed and with maximum safety. An improper trim not only can reduce the efficiency of the boat but can result in a relatively dangerous boating situation where the control of the boat is lost. For example, if proper trim position is not maintained in rough water and, particularly, at high speeds, the steering and speed control is adversely affected. If the boat is being operated in rather shallow water conditions, the unit should, of course, be tilted upwardly.
With automatic power trim positioning, automatic visual indication of the degree of trim is desirable. Various systems have been suggested for stern drives for providing the desired positioning indicating. For example, satisfactory apparatus is shown in U.S. Pat. Nos. 3,834,345 and 3,641,965 for rotary and linear sensing system. U.S. Pat. No. 3,834,345 discloses a linear rotary potentiometer sensor secured to the stern drive's pivot shaft to provide a signal related to the angular orientation of the outboard or of the lower propeller unit. Generally such devices in addition to providing indication of the trim will incorporate a separate limit switch to limit the upward trim angle of the stern dirve unit. Outboard motors have generally included cam operated trim limit switches but have not included trim sensing devices because of space limitations.
The potentiometer is coupled to an indicating gauge to establish a visual indication of the engine trim angle while the limit switch is employed in combination with the trim power positioning apparatus particularly the control circuitry thereof to limit the trim angle to which the engine can be moved by the trim-up control means.
Although such limit controls have provided highly satisfactory indication and interlocking limit of the trim angle they have generally required separate limit switches and indicating signals and have the components mounted to the exterior of the motor asembly.